In the formation of an opthalmic lens, a lens disc or blank is first molded from glass or plastic. This blank is typically fashioned with a convex surface on one side and a concave surface on the other. In order to process the lens to a desired prescriptive value, the lens is then mounted upon a lens generator where a rotating grinding cup, mounted at an angle to a central longitudinal axis of the lens, is swept across the lens to produce a toroidal surface of compound prescriptive value. Illustrative examples of such lens generating equipment are shown in United States patents to Coburn U.S. Pat. No. 2,086,327; Suddarth U.S. Pat. No. 3,449,865; and Suddarth et al. U.S. Pat. No. 3,458,956, all assigned to the assignee of the subject application.
Following the initial generating operation, the opthalmic lens is fined and polished to a final prescriptive value. An illustrative example of an opthalmic lens finer and polisher is shown in a commonly assigned patent to Stith, U.S. Pat. No. 3,732,647. Left and right lenses are then mounted upon an edge grinding machine to cut the outer peripheral shape required of the lens in order to be compatible with eye glass frames. Illustrative examples of opthalmic lens edging machines are shown in United States patents to Grey et al. U.S. Pat. No. 3,121,979; Novak U.S. Pat. No. 3,555,739; Haddock U.S. Pat. No. 4,027,434; and Haddock U.S. Pat. No. 4,203,259, again all assigned to the assignee of the instant application.
After an opthalmic lens has been edged, a sharp ledge exists on the front and back perimeters of the lens. These ledges can be dangerous if they are left exposed, and they also increase the susceptibility of the lens to chipping. Accordingly, after the lens has been edged, the edge surfaces are bevelled to remove their sharp peripheral edges. Traditionally this task has been performed by a skilled individual who bevels the lens edges using a large rotating handstone. However, regardless of the individual's skill, close examination of the finished lens revealed tell-tale start and finish marks, as well as subtle changes in the angles of the bevels. Moreover, hand bevelling added materially to the cost and time required to produce opthalmic lenses.